Kava Fact of the Day The Variation in Acetonic Test Results.

[The Kap'n]

R² Variation In Practical Terms

Yesterday we took the dive of looking at what R² means in relation to the studies we were using for sources. We now understand that R² does not speak for the accuracy of the test to determine between types of kava, but only to variation, and the regression model in question.

Today we’re going to speak about why this number isn’t higher in the tests we’ve been looking at. Essentially we’re addressing what’s causing the absorbance to be higher in some cases when the kava may actually not have high FK levels. In short, we’re addressing the very variation we spoke about yesterday in our R²=0.5211 topic.

Variation in Test Results?

Kava is a rich mixture of a number of different phytochemicals and compounds. No less than 30 different molecules have been identified from the roots, including nineteen kavalactones, three flavokavains, and eight minor compounds [1]. Acetone is used in this preparation due to its strong ability to dissolve fats and oils and compounds which don’t mix well with water. Acetone’s ability to extract compounds doesn’t stop at kavalactones and FKs, and can also remove other compounds in the plant. Unidentified pigments in the peelings and chlorophyll are also extracted by strong solvents. These other compounds can cause a variation in the resulting absorbance (V. Lebot, personal communication, May 18, 2021). This tells us that poor preparation can also cause a dark result (higher absorbance) in the acetonic test. For example Isa, if only the rhizome is used and it is peeled meticulously, when tested, the absorbance spectra will say the kava is noble. This is suspected to be due to high FK content in the peelings.

What does this mean?

Kavas that result in a high absorbance have several possible categories instead of simply high quality and low quality due to the variables in the coefficient of determination. These classifications are:

For When the Absorbance is high (strong color result)

1. The kava is: Non-noble / Non-beverage grade
2. The kava is: Noble, but has not been properly peeled or has contaminants such as soil or upper portions of the kava plant mixed in.
3. The kava is: Non-noble and has not been properly peeled or has contaminants such as soil or upper portions of the plant mixed in.
4. The kava is: Noble consisting of a high proportion of proximal lateral roots of certain varieties.
5. The kava is: Noble or Non-noble and has been dried at an excessively high oven temperature.

(#4 & #5 added with the help of @verticity)
​

For when the absorbance is low (Very yellow result)(Clarification thanks to @verticity)

1. The kava is: Noble and properly peeled (most likely)
2. The kava is: Non-Noble with low FK content and properly peeled (less likely but entirely possible)

What this tells us is that if a kava returns a poor result from a colorimeter with the acetonic test, it’s best to send that sample to a lab which uses HPLC or another accepted analytical method to determine exactly what is going on with that sample. Just as we’ve said before, this test is excellent to make a quick initial determination of product quality.

Does this method work at home?

Here’s where we get into some problems where others have raised issues before. You can run this test yourself at home with kavas, however our eyes are NOT colorimeters. The difference between noble kava and wild kavas in terms of acetonic tests is stark and quite obvious to the untrained eye. The difference between some 100% noble kavas and some non-noble kavas can be very slight. Unless you’re superhuman, I doubt one can identify exactly the wavelength of light by looking at it. It’s best to let the machines make the determinations here.

Summary:

There is a misunderstanding that coefficient of determination means “overall accuracy of this test”. It does not. The acetonic test is actually quite accurate, but, as mentioned, does have its shortcomings. This is a relatively new science with kava, and as we go forward researchers will continue to add more and more evidence towards the viability of this test just as we’ve seen here.



Lebot, V., T. K. T. Do, and L. Legendre. 2014. “Detection of Flavokavins (A, B, C) in Cultivars of Kava (Piper Methysticum) Using High Performance Thin Layer Chromatography (HPTLC).” Food Chemistry 151 (May): 554–60.
https://doi.org/10.1016/j.foodchem.2013.11.120.

 

[verticity]

In my opinion, for the little that my opinion is worth on this topic:

I do agree that the acetone test is extremely useful as a rough quality screen and has done much to improve the quality of kava exported from Vanuatu. I'm in favor of it's use until they can come up with something better that is cost effective.

I would just add a couple points to the above.

There are at least 2 additional ways that a high absorbance can be observed. Both are probably rare in practice.

4. The kava is: Noble consisting of a high proportion of proximal lateral roots of certain varieties.
5. The kava is: Noble or Non-noble and has been dried at an excessively high oven temperature.

Also, I think it is important to note that although noble kava is nearly always yellow when properly prepared, the converse is not true. It is sometimes possible for non-noble kava to appear yellow in the test. Most Non-noble kava is high in FKs, but not all. It's on a bell curve, and low-FK non-noble stumps can slip through the test. You might say that doesn't matter because FK is the bad thing we want to avoid, but that non-noble kava tends to have an undesirable kavalactone profile, so just be aware the acetone test is not infallible at catching all tudei. As Lebot himself has said the only way to really be sure is to do genetic testing. The acetone test by itself is just not capable of guaranteeing that kava is a noble variety.

So there would be a corresponding list for the case where the absorbance is low:

What does it mean if the absorbance is low in the test?

There are two possible categories:

1. The kava is: Noble and properly peeled (most likely)
2. The kava is: Non-Noble with low FK content and properly peeled (less likely but entirely possible)

 

[The Kap'n]

In my opinion, for the little that my opinion is worth on this topic:

I do agree that the acetone test is extremely useful as a rough quality screen and has done much to improve the quality of kava exported from Vanuatu. I'm in favor of it's use until they can come up with something better that is cost effective.

I would just add a couple points to the above.

There are at least 2 additional ways that a high absorbance can be observed. Both are probably rare in practice.

4. The kava is: Noble consisting of a high proportion of proximal lateral roots of certain varieties.
5. The kava is: Noble or Non-noble and has been dried at an excessively high oven temperature.

Also, I think it is important to note that although noble kava is nearly always yellow when properly prepared, the converse is not true. It is sometimes possible for non-noble kava to appear yellow in the test. Most Non-noble kava is high in FKs, but not all. It's on a bell curve, and low-FK non-noble stumps can slip through the test. You might say that doesn't matter because FK is the bad thing we want to avoid, but that non-noble kava tends to have an undesirable kavalactone profile, so just be aware the acetone test is not infallible at catching all tudei. As Lebot himself has said the only way to really be sure is to do genetic testing. The acetone test by itself is just not capable of guaranteeing that kava is a noble variety.

So there would be a corresponding list for the case where the absorbance is low:

What does it mean if the absorbance is low in the test?

There are two possible categories:

1. The kava is: Noble and properly peeled (most likely)
2. The kava is: Non-Noble with low FK content and properly peeled (less likely but entirely possible)

Your opinion is worth a ton to me. Would you mind if I incorporated your part into my fact of the day across the platforms as to more closely mirror the reality of things?

 

[verticity]

Your opinion is worth a ton to me. Would you mind if I incorporated your part into my fact of the day across the platforms as to more closely mirror the reality of things?

Thanks. Sure, incorporate away.. Very nice job with these write ups btw..

 

[TheKavaSociety]

In my opinion, for the little that my opinion is worth on this topic:

I do agree that the acetone test is extremely useful as a rough quality screen and has done much to improve the quality of kava exported from Vanuatu. I'm in favor of it's use until they can come up with something better that is cost effective.

I would just add a couple points to the above.

There are at least 2 additional ways that a high absorbance can be observed. Both are probably rare in practice.

4. The kava is: Noble consisting of a high proportion of proximal lateral roots of certain varieties.
5. The kava is: Noble or Non-noble and has been dried at an excessively high oven temperature.

Also, I think it is important to note that although noble kava is nearly always yellow when properly prepared, the converse is not true. It is sometimes possible for non-noble kava to appear yellow in the test. Most Non-noble kava is high in FKs, but not all. It's on a bell curve, and low-FK non-noble stumps can slip through the test. You might say that doesn't matter because FK is the bad thing we want to avoid, but that non-noble kava tends to have an undesirable kavalactone profile, so just be aware the acetone test is not infallible at catching all tudei. As Lebot himself has said the only way to really be sure is to do genetic testing. The acetone test by itself is just not capable of guaranteeing that kava is a noble variety.

So there would be a corresponding list for the case where the absorbance is low:

What does it mean if the absorbance is low in the test?

There are two possible categories:

1. The kava is: Noble and properly peeled (most likely)
2. The kava is: Non-Noble with low FK content and properly peeled (less likely but entirely possible)

excellent comments.
Re some thin laterals: this is probably linked to the fact that the skin represents a very high % of the overall mass, plus they are also quite hard to clean. Which brings me to another point: kava that is covered in foreign matter (soil, dust, etc etc) might also fail the test.

 

[Zaphod]

You might say that doesn't matter because FK is the bad thing we want to avoid, but that non-noble kava tends to have an undesirable kavalactone profile, so just be aware the acetone test is not infallible at catching all tudei. As Lebot himself has said the only way to really be sure is to do genetic testing. The acetone test by itself is just not capable of guaranteeing that kava is a noble variety.

This is something that has bugged me since the very beginning. It has never been clear what about "Tudei" (I put it in quotes because there are many different definitions - some based on genetic cultivar and some based on FK content and some on various KL %) makes it undesirable. Is it FK content? Is it FK% relative KL%? Or is it not FK at all and FK is just somewhat imprecise indicator of a undesirable KL mixing (i.e. low 4 high 6/2). Until we define what we want to avoid using a tudei label it is a very poor indicator of quality control in any deterministic sense.

That said avoiding kavas that make people physically ill and keeping them off the market is a good thing (some might even say a noble pursuit ), and should be pursued.

 

[verticity]

This is something that has bugged me since the very beginning. It has never been clear what about "Tudei" (I put it in quotes because there are many different definitions - some based on genetic cultivar and some based on FK content and some on various KL %) makes it undesirable. Is it FK content? Is it FK% relative KL%? Or is it not FK at all and FK is just somewhat imprecise indicator of a undesirable KL mixing (i.e. low 4 high 6/2). Until we define what we want to avoid using a tudei label it is a very poor indicator of quality control in any deterministic sense.

That said avoiding kavas that make people physically ill and keeping them off the market is a good thing (some might even say a noble pursuit ), and should be pursued.

The fundamental definitions of "noble" and "tudei" are not ambiguous. Noble is defined as the cultivars that people in Vanuatu traditionally recognized as suitable for daily drinking. Non-noble is defined as everything else, and "tudei" is a large subset of non-noble kava, again defined by traditional knowledge of cultivars with longer acting, more sedating, and often unpleasant side effects that are not suitable for daily drinking. Noble and tudei varieties are identifiable by their morphology when they are growing in the ground, or by their genetic makeup. European scientists such as Lebot discovered that noble and tudei varieties usually have distinct kavalactone profiles and that noble kava is usually much lower in flavokavains than tudei varieties, but those European scientists and chemical properties don't define what noble and tudei mean. And noble kava on average is high in the desirable chemicals and low in the undesirable ones. For the majority of intents and purposes what the desirable and undesirable components are is not myterious either: FKs are undesirable and Kavain is the most desirable KL. (Yes, that is hugely oversimplified, but I'm talking about averages and what most people usually want the most of.) But the kavalactone and FK profiles are secondary characteristics with a lot of variability. Both lie on bell curves. So although most tudei kava is high in FKs, the bell curve overlaps the noble bell curve, so in certain cases they are indistinguishable if you only measure the secondary chemical properties. But still, on average, tudei is higher in undesirable things, and low in desirable KLs. It is possible to ruin noble kava by not peeling it, harvesting it too early, etc. And it is also possible to find samples of tudei that are drinkable. But going by statistics, as a consumer I want to purchase kava that will be good with favorable effects, so my best bet, statistically speaking, is to purchase noble kava and avoid tudei as much as possible. From an exporting country's perspective: they want to put their best foot forward and only export the good stuff, properly prepared, free of contaminants, for many reasons of simple economics. public health, national pride, etc. So Vanuatu has decided to do their best to export only noble kava with the imperfect tools at their disposal. I support that, and also hope that in the future they find better tools such as genetic testing to do a better job of controlling their exports for their and our benefit.

 

[Alia]

Noble is defined as the cultivars that people in Vanuatu traditionally recognized as suitable for daily drinking

Glad you brought this up and it may have been discussed before. As indeed Vanuatu is where the term Noble was invented.
Since then all or most all other kava drinking regions of the Pacific have adopted the term to describe their own
cultivars with historic, safe, use. As anyone who has read the Codex alimentarius Kava Standards will see, each region
contributed their own lists of Noble kava.